Cambrian: Opinion

Tagged elephant seal pups are returning to Piedras Blancas. Here’s what the data tells us

Two elephant seals that were tagged as weaned pups at Año Nuevo showed up at Central Coast beaches last weekend. Friends of the Elephant Seal docents, with home-made electronic antennas, guided the researchers to their wild quarry.

“We simply would not have recovered our diving and tracking data without this partnership between UCSC researchers and citizen scientists from Friends of the Elephant Seal,” said Dr. Roxanne Beltran, a post-doctoral researcher in Dr. Dan Costa’s Lab at UC Santa Cruz.

The data recorders they carried will tell researchers where the seals have been for the past 15 months. But first, the seals had to return, and the researchers had to find them and retrieve the devices. Fewer than half seal pups survive their first migration, and they may not return to the beach where they were born.

The numbers aren’t good.

Dr. Beltran tagged 24 pups in 2018 as part of a National Geographic grant. Pups may return from their first migration as early as September, but none of the tagged seals showed up in 2018. In December, two tagged seals hauled themselves out onto the beach at Point Reyes.

With help from an observant beach visitor and a park ranger off duty due to the government shutdown, they found the seals and retrieved those tags. Two is far less than even half of the 24 they’d tagged. They waited for reports of more.

FES has a Citizen Science program, enlisting docents in projects overseeing the seals. FES Board Vice President Kathy Curtis got information from the UCSC research team and asked docents to keep an eye out for them. Docents Leo and Peggy Dewinter, Keith Mueller and Carol Kirkpatrick joined in.

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Leo Dewinter made an antenna to track the tagged seals. Courtesy photo

Docents are out on the bluff every day, looking at the seals. The devices aren’t obvious, but careful observers can see them. After many days of searching, no instrumented seals had been seen. Leo Dewinter, retired from a career in electronics and holding a ham radio license since 1976, decided to add radio tracking to visual observation.

He used his skills to build an antenna out of PVC and metal rods he bought at Home Depot. He tuned it to the frequency the seals’ devices transmit and hooked it to his receiver. He took extra hours after his regular docent shift to scan the beach for those missing seals.

On Friday, May 10, one of the seals’ GPS reported to the researchers that a seal was in the Piedras Blancas area. With his antenna, Dewinter was able to home in on the seal, near the old motel. Two researchers, Arina Favilla and Rachel Holser, came down and retrieved the device. But Dewinter heard a second, mysterious ping.

Working with docent Phil Arnold on the spotting scope, they found a second seal — one of the missing weanlings carrying data-filled instruments. Dr. Beltran and her husband, Año Nuevo Natural Reserve director Dr. Patrick Robinson, dropped everything to drive south to find the seal. They were able to retrieve the device, which they brought to the FES docent dinner meeting this month.

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Phil Arnold, with his spotting scope, and Patrick Robinson, showing the retrieved device. Roxanne Beltran Courtesy photo

They were feted as honored guests, to cheers all around. They wanted to honor Dewinter for his work by naming the seal for him, but as it is a female seal, they named her for Leo’s wife, Peggy. The researchers raced back to Santa Cruz and downloaded the data.

“The weanling seal held her breath for four minutes on the very first dive, and by the second day of the migration dove for an average of 10 minutes,” Dr. Beltran said. “We are learning that these young seals develop their diving abilities very quickly, which allows them to find food and survive their first migration.”

Follow the project’s progress at the blog,